const arr = [1, 2, 3, 4, 5, 6, 5, 1];
// let newArr = ['a', 'b', 'c', 'd', 'e'];

// newArr = arr.concat(newArr);
// arr.push(...newArr);// == newArr=['a','b','c','d','e',...arr]
// console.log(newArr);

arr.sort((a, b) => {
    return a - b;
})
console.log(arr);
